A conveyor belt is extremely useful as a means for transporting articles, and is used in many places.
The conveyor belt comprises generally an upper cover rubber, a reinforcing material and a lower cover rubber. In particular, the upper cover rubber may be readily worn by the friction against the object mounted thereon to be conveyed, and, for example, when given an impact by the corner of the object to be conveyed, there is a fear that the upper cover rubber may be cracked. Consequently, for the purpose of prolonging the life of the entire belt, it is necessary to satisfy both wear resistance and cutting resistance.
Of the above-mentioned performances, for improving the cutting resistance and the impact resistance, there is disclosed a rubber composition for conveyor belt covers, which contains from 45 to 65 parts by mass of carbon black having a nitrogen adsorption specific surface area of 100 m2/g or more and a DBP oil absorption of 100 cm3/100 g or more, from 5 to 20 parts by mass of silica, and from 2 to 7 parts by mass of resin, relative to 100 parts by mass of rubber therein having a blend ratio (by mass) of natural rubber to styrene-butadiene rubber of from 50/50 to 80/20 (see PTL 1). However, the rubber composition is still unsatisfactory in point of wear resistance.
Contrary to this, for satisfying both wear resistance and cutting resistance, there is disclosed a rubber composition for conveyor belts, which contains, relative to (A) 100 parts by mass of a rubber component therein containing from 90 to 60 parts by mass of styrene-butadiene rubber and from 10 to 40 parts by mass of butadiene rubber and/or natural rubber, (B) from 50 to 70 parts by mass of carbon black having a nitrogen adsorption specific surface area of 100 m2/g or more and (C) from 10 to 30 parts by mass of a resin (see PTL 2). The rubber composition could be improved in some degree in point of both the impact resistance and the cutting resistance thereof, but there is still room to improve the cutting resistance, and moreover, the rubber composition has another problem in that the production workability thereof is poor.